Chanyeol and Naeun are just a normal bestfriend at first. But they don't treat each other like normal friends do. They're more likely to treat each other like their own brother/sister. They know each other's secret. But not with this one that each of them have, no one knows it, and most importantly they don't even know. Then many things happen, somehow this brother-sisterly love brings them to each other's destiny. They don't even know why and how, they don't even ask and just follow their path like how the river flows. But then, the happiness won't let them to have it forever. What will happen when the happiness they have choose to leave?